Semiconductor device with reduced interconnection capacity

ABSTRACT

This invention provides a semiconductor device that can ensure that stress on the nitride film is not increased or is reduced, and that can prevent an increase in interconnection capacity. The semiconductor device comprises a underlayer, a base oxide film that is formed on this underlayer, a nitride film pattern with a hole pattern that is provided on this base oxide film, holes that penetrate the base oxide film, an upper oxide film provided on the base oxide film to cover the nitride film pattern, wiring grooves provided through the upper oxide film in which part of the nitride film pattern including the hole pattern is exposed, and wiring metal that fills the holes and wiring grooves. The nitride film pattern is formed with such a shape and size that surrounds the outside of the wiring grooves and is separate from neighbouring nitride film patterns.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device structure andits manufacturing method, and more particularly to a manufacturingmethod for a semiconductor device that uses a dual damascene process inwhich a metal material is embedded into both a wiring groove and a holeused for the contact between lines.

2. Description of Related Art

Recent years have seen the need for acceleration of semiconductordevices such as LSIs and a trend towards much smaller devices. However,attempts to speed up smaller devices are hampered by line delays. Use oflow resist Cu line instead of the conventional Al line is proposed tosolve this problem of line delays.

It is difficult to use the dry etching process used when forming Al lineon Cu film (or layer) when forming the Cu line. Therefore, the Cu lineis formed in a damascene process in which Cu is embedded in a grooveprovided in an insulation film. The emergence of a dual damasceneprocess in which the metal can be embedded simultaneously in both thewiring groove and in the hole provided for contact between wires meansthat the number of processes can be reduced compared to the numberinvolved in forming Al line using dry etching. Therefore, the cost ofline manufacture can be reduced.

Below, some of the processes involved in the manufacturing method forordinary semiconductors using the dual damascene process will be brieflyexplained with reference to FIGS. 24(A)-24(E) through 27.

FIG. 24(A)-24(E) shows the manufacturing processes used for aconventional semiconductor device when the dual damascene process isused. FIG. 24(E) shows a section through the line I—I on FIG. 27. FIG.27 is a plan view of the semiconductor device as viewed from above afterline has been formed. FIG. 25 is a plan view of the mask used for holeformation and FIG. 26 is a plan view of the mask used for line patternformation.

Firstly, after a base oxide film 102 is formed on an Si substrate 100, anitride film 104 is formed on this base oxide film 102. Next, afterproviding a resist on the nitride film 104, photo lithography isimplemented using the mask for hole formation 106 shown in FIG. 25. Ahole shaped window 108 is provided in the mask 106. This enables theformation of a resist pattern 110 that corresponds to the hole shape(FIG. 24(A)). This resist pattern 110 is then used as a mask for etchingthat penetrates the nitride film 104. This enables formation of the holepattern 112 through the nitride film 104 and exposure of the base oxidefilm 102 from the hole pattern 112 (FIG. 24(B)). Next, an upper oxidefilm 114 is provided on the remaining nitride film 104 x and the exposedbase oxide film 102 (FIG. 24(C)). Then, after a resist has been providedon the upper oxide film 114, the resist undergoes photo lithographyprocessing with the use of the mask 116 for line pattern formation asshown in FIG. 26. This mask 116 is provided with a window 118 in theshape of the wire (or line) pattern. This provides the resist pattern120. The upper oxide film 114 is then etched using this resist pattern120 as a mask. Following etching, the remaining nitride film 104 x isused as a mask for etching of the base oxide film 102. This forms acontact hole 122 so as to penetrate the base oxide film 102 and toexpose the surface of the Si substrate 100. At the same time, a wiringgroove 124 in the shape of the line pattern can also be formed (FIG.24(D)). The wiring metal 126 is next embedded in the contact hole 122and in the wiring groove 124 using a spatter method or plating (FIGS.24(E) and 27). The surface of the embedded metal 126 is then flattenedusing chemo-mechanical polishing (CMP) and polished until it is, inpractice, level with the surface of the upper oxide film 114. Thus, thecontact between interconnections and the interconnection itself can beformed.

However, the nitride film 104 x used as the etching mask used for thebase oxide film 102 is generally known to have a high dielectricconstant and be highly subject to stress. When the nitride film is madethicker to improve its durability in etching or when it is subject toheat processing in later processes in the manufacture of thesemiconductor device, the stress placed on it increases. This causesproblems such as cracks in the nitride film or deformation of the holepattern formed in the nitride film. Also, the thicker the nitride film,the greater the interconnection capacity, the cause of line delays.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide asemiconductor device in which increased interconnection capacity can beprevented and in which the stress that the nitride film is subject tocan be limited or decreased. The other object of the present inventionis to provide a manufacturing method for semiconductors that avoids theeffect of stress on the nitride film during manufacture.

In order to attain the above-mentioned object, the semiconductor deviceof the present invention has a underlayer, a base oxide film with holesthat is formed on this underlayer, a nitride film pattern with a holepattern that is formed on the base oxide film directly over the holes,an upper oxide film formed on the base oxide film to cover the nitridefilm pattern, the upper oxide film having formed therethrough a wiringgroove wherein part of the nitride film pattern that includes the holepattern is exposed, and lines that are embedded in the hole and wiringgroove. The above nitride film pattern is formed with a shape and sizesuch that its perimeter surrounds the outside of the wiring grooves anddoes not come into contact with any neighbouring nitride film patterns.

This structure allows the nitride film pattern to be formed with a shapeand size that encloses the perimeter of the bottom of the wiring groove.If, in the configuration of the semiconductor device, a plurality ofstructures with wiring grooves and holes are provided separately, thenitride film pattern is formed with a size and shape that preventsneighbouring nitride film patterns from coming into contact with oneanother. That is, the perimeter of the nitride film pattern is onlyslightly larger than the size of the bottom of the wiring groove andtherefore much smaller than the total area of the base oxide film.Therefore, the stress placed on the nitride film can be reduced and asemiconductor device made with a low interconnection capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will be better understood from the following description takenin connection with the accompanying drawings, in which:

FIG. 1(A) to 1(C) are diagrams that overview the processes involved inthe manufacture of a semiconductor in a first embodiment of the presentinvention and shows a cross-section through the structure;

FIGS. 2(A) through 2(C) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 1;

FIGS. 3(A) and 3(B) are a plan view and corresponding cross-sectionalview schematically showing the semiconductor device of FIG. 2:

FIG. 4 is a general schematic view of the mask used in photolithography;

FIGS. 5(A) through 5(C) are general diagrams of the processes involvedin the manufacture of a semiconductor device in a second embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 6(A) through 6(C) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 5;

FIGS. 7(A) and 7(B) are a plan view and corresponding cross-sectionalview schematically showing the second embodiment of a semiconductordevice:

FIGS. 8(A) through 8(D) are general diagrams of the processes involvedin the manufacture of a semiconductor device in a third embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 9(A) through 9(C) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 8;

FIGS. 10(A) and 10(B) are a plan view and corresponding cross-sectionalview schematically showing the third embodiment of a semiconductordevice,

FIGS. 11(A) through 11(D) are general diagrams of the processes involvedin the manufacture of a semiconductor device in a fourth embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 12(A) through 12(C) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 11;

FIGS. 13(A) and 13(B) are a plan view and corresponding cross-sectionalview schematically showing the fourth embodiment of a semiconductordevice:

FIGS. 14(A) through 14(D) are general diagrams of the processes involvedin the manufacture of a semiconductor device in a fifth embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 15(A) through 15(D) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 14;

FIGS. 16(A) and 16(B) are a plan view and corresponding cross-sectionalview schematically showing the fifth embodiment of a semiconductordevice;

FIGS. 17(A) through 17(C) are general diagrams of the processes involvedin the manufacture of a semiconductor device in a sixth embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 18(A) through 18(D) are also diagrams of the processes involved inthe manufacture of a semiconductor device and continue on from FIG. 17;

FIGS. 19(A) and 19(B) are a plan view and corresponding cross-sectionalview schematically showing the sixth embodiment of a semiconductordevice:

FIG. 20 is a general schematic view of the mask used in photolithography;

FIGS. 21(A) and 21(B) are general diagrams of the processes involved inthe manufacture of a semiconductor device in a seventh embodiment of thepresent invention, and show cross-sections through the structure;

FIGS. 22(A) and 22(B) are a plan view and corresponding cross-sectionalview schematically showing the seventh embodiment of a semiconductordevice;

FIGS. 23(A) through 23(D) are general diagrams of the processes involvedin the manufacture of a semiconductor device in an eighth embodiment ofthe present invention, and show cross-sections through the structure;

FIGS. 24(A) through 24(E) are diagrams showing the processes involved inthe manufacture of conventional semiconductors;

FIG. 25 is a plan view of the mask used in hole formation that is usedto explain the conventional art;

FIG. 26 is a plan view of the mask used in line pattern formation thatis used to explain the conventional art; and

FIG. 27 is a plan view of a conventional semiconductor device as viewedfrom above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to drawings, embodiments of the present invention willhereinafter be explained. The figures are only overviews of the shape,size, and arrangement of components to help provide an understanding ofthe invention and accordingly, the present invention is not limited tothe examples pictured. Furthermore, to further clarify the diagrams,hatching to show a cross-section has been omitted except for part ofcomponents.

First Embodiment

With reference to FIGS. 1 through 4, an example of the manufacture of asemiconductor using the dual damascene process will be explained as afirst embodiment of the present invention.

FIGS. 1 to 3 give overviews of the processes involved in the manufactureof semiconductor devices in the embodiment of the present invention.They provide cross sections taken at positions on the structure duringmanufacture that have both a hole for a contact between lines and agroove for a line. FIG. 4 is a general schematic view of the mask usedin photo lithography processing.

Firstly, a base oxide film 12 as a lower oxide film is formed on aunderlayer 10 (process 1-1) (FIG. 1(A)).

In this example, the CVD method is used to form an SiO₂ film, which isthe base oxide film 12, of between 500 and 800 nm in depth on the Sisubstrate 10 used as the underlayer.

Next, a nitride film pattern 16 with a hole pattern 14 is formed on thebase oxide film 12 (process 1-2) (FIGS. 1(A) and 1(B)).

In this example, the CVD method is used to form an Si₃N₄ film, as thenitride film 16 x, on the SiO₂ film 12. A resist film is then placed onthe Si₃N₄ film 16 x and, using commonly used photo lithographytechnology, a resist pattern 18 that corresponds to the nitride filmpattern is formed (FIG. 1(A)).

The configuration of the mask 20 used in this photo lithography is shownin FIG. 4. This mask 20 comprises a transparent mask substrate 21, aline pattern 22 on this mask substrate 21 of a width W2 that is between0.2 and 1.0 m larger than the width W1 of the line provided later, and ahole pattern 24 for contacts between lines. There is a plurality of linepatterns and each runs parallel to the others. There are also as manyhole patterns 24 as required. In this example, the line width W1 isbetween 0.25 and 1.0 m and the hole diameter is between 0.1 and 0.5 m.The device is designed to ensure that the hole diameter is never largerthan the line width W1.

In this example, a resist pattern 18 that corresponds to the shape ofthe nitride film pattern is formed by etching the resist film using thismask 20 (FIG. 1(A)). A nitride pattern 16 with a hole pattern 14 that isbetween 0.2 and 1.0 m larger than the line width W1 but much smallerthan the size of the upper surface of the SiO₂ film 12, is then obtained(FIG. 1(B)).

Next, an upper oxide film 26 is formed on the base oxide film 12 tocover the nitride pattern 16 (process 1-3) (FIG. 1(C)).

In this example, the CVD method is used to form an upper oxide film 26of SiO₂ of between 500 and 800 nm in depth on the base oxide film 12(FIG. 1(C)).

Next, a wiring groove 28 that penetrates the upper oxide film 26 toexpose the nitride film pattern 16, and holes 30 that penetrate the baseoxide film 12 and expose part of the substrate 10 using the nitride filmpattern 16 as a mask are continuously formed in etching (process 1-4)(FIGS. 2(A) and (B)).

In this embodiment of the present invention, after the resist film isformed on the upper oxide film (SiO₂ film) it is patterned to form aresist pattern 34 in which the wiring groove pattern becomes the window32. Next, the resist pattern 34 is used as a mask in dry etching usingC₄F₈/O₂/Ar gases which etches the upper oxide film 26 that is exposedfrom the window 32. Also, the dry etching used is anisotropic etching inwhich medium density plasma (with a plasma density of between 10¹¹ and10¹² cm⁻³) is used. Etching of the upper nitride film 26 ends when thesurface of the nitride film pattern 16 lying between the upper oxidefilm 26 and base oxide film 12 is exposed (FIG. 2(A)). After this, thebase oxide film 12 that has been exposed from the hole pattern 14 isetched with the nitride film pattern 16 that has been exposed from thebottom of the opening in the upper oxide film 26 being used as a mask.Etching of the base oxide film 12 ends when the surface of the Sisubstrate 10 is exposed from the hole pattern 14. The wiring groove 28and hole 30 are formed through this process (FIG. 2(B)).

Next, the wiring metal 36 is embedded in the hole 30, on part of thearea of the exposed nitride film pattern 16, and in the wiring groove 28(process 1-5: dual damascene process) (FIG. 2(C)).

FIG. 3(A) shows a partial plan view of a semiconductor device obtainedaccording to the process mentioned above with reference to FIGS. 1 and2.

FIG. 3(B) shows a cross-sectional view taken along the line I—I of FIG.3(A).

In this example, after for example a 50 nm thick barrier metal layer 35is formed in the hole 30 and groove 28 using the CVD method, plating isused to embed Cu 36 in the hole 30 and wiring groove 28. When the hole30 has been completely filled with the barrier metal layer 35, the Cu 36can be embedded just into the wiring groove 28 in which case the spattermethod can be used. Also, in this example, Cu was used as the wiringmetal 36 to lower the line capacity. However, Al alloys can also be usedas the metal for lines and contacts between lines.

Next, CMP processing of the part in which the Cu 36 is embedded is usedto form the contact between lines and the metal lines (FIG. 2(C)).

As a result, as is clear from the above explanations, the nitride filmpattern 16 is formed to be between 0.2 and 1.0 m larger than the openingof the wiring groove 28. Accordingly, as in conventional methods, in theetching that forms the wiring groove 28 and the hole 30, after etchingof the upper oxide film 26 ends, the nitride film pattern 16 acts as anetching mask to protect the base oxide film 12 so that it is not exposedexcept within the hole pattern 14.

The nitride film pattern 16 is provided only where necessary on the baseoxide film 12 and therefore is smaller than in conventionalsemiconductor devices. Accordingly, the stress placed on the nitridefilm pattern 16 is less than in conventional devices. This enables thedeformation of formed holes and cracks in the nitride film caused bystress to be avoided.

Second Embodiment

With reference to FIGS. 5, 6 and 7, an example of the formation of anitride film pattern using a method different to that used in the firstembodiment will be explained as a second embodiment of the presentinvention.

FIGS. 5 and 6 provide overviews of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. They provide cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line.

FIGS. 7(A) and 7(B) show a partial plan view of a semiconductor deviceof the second embodiment of the Present invention and a cross-sectionalview taken along the line I—I of FIG. 7(A) respectively.

Below, those points that differ from the first embodiment will beexplained and detailed explanation of those points that are the same, asthe first embodiment will be omitted.

Firstly, the base oxide film 12 is formed on the substrate 10 (process2-1) (FIG. 45(A)).

In this example, as with the first embodiment, the CVD method is used toform an SiO₂ film 12 of between 500 and 800 nm in depth on the Sisubstrate 10. Next, a groove 42 for nitride film pattern formation isformed within the area of the base oxide film 12 (process 2-2) (FIGS.5(A) and 5(B)).

In this example, firstly a resist film is formed on the SiO₂ film 12.The resist pattern 44 is then formed by photo lithography using a maskthat is the reverse of the mask in FIG. 3 (FIG. 5(A)). The resistpattern 44 thus obtained has a line shaped window 46 that is between 0.2and 1.0 m wider than the line width W1 and a hole shaped island 48formed in this window 46. This resist pattern 44 can also be formed asfollows. That is, a negative resist can be provided on the SiO₂ film 12and photo lithography implemented using the same mask 20 as in FIG. 4(FIG. 5(A)).

Next, this resist pattern 44 is used as a mask for etching of the SiO₂film 12 to form a groove 42 for forming a nitride film pattern ofbetween 100 and 300 nm in depth. This etching causes an island 40 in theshape of the hole pattern to remain within the groove 42 for the nitridefilm pattern formation, that is an island enclosed by the groove (FIG.5(B)).

Next, the material for the nitride film is embedded in the groove 42 forforming the nitride film pattern and a nitride film pattern 50 with ahole pattern 50 x is formed (process 2-3) (FIG. 5(C)).

In this embodiment of the present invention, firstly material for thenitride film is embedded in the groove 42 for forming the nitride filmpattern. Then, CMP processing of this nitride film material isimplemented. This enables a nitride film pattern 50 that is between 0.2and 1.0 m wider than the line width W1 and that has a hole pattern 50 xto be formed in the groove 42 (FIG. 5(C)).

Next, an upper oxide film 26 is formed on the base oxide film 12 thatincludes the nitride film pattern 50 (process 2-4) (FIG. 6(A)).

In this example, the CVD method is used to form an SiO₂ film of between500 and 800 nm in depth as the upper oxide film 26 on the base oxidefilm (SiO₂ film) (FIG. 6(A)).

Next, the same etching processing is used to continuously form a wiringgroove 28 and holes 30. The wiring groove 28 penetrates the upper oxidefilm 26 to expose part of the nitride film pattern 50, which includesthe hole pattern 50 x. The holes 30 penetrate the base oxide film withinthe hole pattern 50 x to expose part of the substrate 10 (process 2-5)(FIG. 6(B)).

The wiring metal 36 is then embedded into the holes 30, part of the areaof the exposed nitride film pattern 50, and the wiring groove 28 (2-6)(FIG. 6(C)).

In this example, as in the first embodiment, after the resist pattern34, which has a window 32 in the shape of the wiring groove pattern, hasbeen formed on the upper oxide film 26, dry etching is performed usingthis resist pattern 34 as the mask (FIG. 6(B)). Then, after the CVDmethod is used to form the barrier metal layer 35 inside the hole 30 andwiring groove 28 formed by dry etching, plating is used to embed Cu, asthe wiring metal 36, in this wiring groove 28 and hole 30. Then, byimplementing CMP processing of the Cu 36 surface exposed from the wiringgroove, the height of the surface of the Cu 36 can be made the same asthe height of the upper surface of the upper oxide film 25. The contactbetween lines and the metal lines can be formed through the aboveprocesses (FIG. 6(C)).

Consequently, as is made clear in the above explanations, as in thefirst embodiment, the nitride pattern 50 with its width W2 is formed toa size whereby its perimeter encloses the wiring groove 28. Morespecifically, it is formed to a size that is between 0.2 and 1.0 mlarger than the width W1 of the wiring groove opening (FIGS. 6(C), 7(A)and 7(B)). Accordingly, in the etching that forms the wiring groove 28and hole 30, after etching of the upper oxide film 26 ends the nitridepattern 50 acts as the etching mask to protect the base oxide film 12 asin conventional methods, without exposing the base oxide film exceptwithin the hole pattern 50 x.

The nitride film pattern 50 is established only where it is needed onthe base oxide film 12, as in this embodiment, and it can be madesmaller than in conventional semiconductor devices. Accordingly, thestress on the nitride film pattern 50 can also be reduced. This enablesdeformation of formed holes and cracks in the nitride film caused bystress to be avoided.

Third Embodiment

With reference to FIGS. 8, 9 and 10, an example of the formation of anitride film pattern using a method different to that used in either thefirst or second embodiment will be explained as a third embodiment ofthe present invention.

FIGS. 8 and 9 provide overviews of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. They provide cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line.

FIGS. 10(A) and 10(B) show a partial plan view of a semiconductor deviceof the third embodiment of the present invention and a cross-sectionalview taken along the line I—I of FIG. 10(A), respectively.

Below, those points that differ from the first and second embodimentswill be explained and detailed explanation of those points that are thesame as the first and second embodiments will be omitted.

Firstly, the base oxide film 12 is formed on the substrate 10 process3-1) (FIG. 8(A)).

In this example, as in the first and second embodiments, the CVD methodis used to form an SiO₂ film 12 of between 500 and 800 nm in depth onthe Si substrate 10.

Next, a groove 52 with a opening shaped in the same way as the wiringgroove to be formed later is formed on the base oxide film 12 (process3-2) (FIG. 8(B)).

In this example, firstly a resist film is formed on the SiO₂ film 12.Then a mask with a window pattern that is the same shape and size as thewiring groove to be formed later is used in photo lithography processingfor this resist film to form the resist pattern 54 (FIG. 8(A)). Next,this resist pattern 54 is used as a mask in the etching of the SiO₂ film12 to form a groove 52 of a depth between 100 and 300 nm (FIG. 8(B)).

Next, a nitride film 56 x is formed on the base oxide film 12 includingwithin the groove 52 (process 3-3) (FIG. 8(C)).

In this example, an Si₃N₄ film, as the nitride film 56 x, is formed onthe base oxide film 12, including the groove 52, to a depth of between150 and 300 nm.

Next, the nitride film 56 x is etched so that the hole pattern is formedsubstantially in the centre of the groove 52 and of a size and shapethat ensures that it encloses the groove 52. This forms a nitride filmpattern 56 with a hole pattern 64 (process 3-4) (FIGS. 8(C) and 8(D)).

In this example, as in the first embodiment of the present invention, aresist film is provided on the nitride film 56 x and photo lithographyprocessing is implemented using the same mask as in FIG. 4. Thisprovides the resist pattern 58 that corresponds to the shape of thenitride film pattern. The resist pattern 58 has a line pattern of awidth W2, which is between 0.2 and 1.0 m larger than the width W1 of theline to be formed later, and a hole pattern 62 for the contact betweenlines (FIG. 8(C)).

The resist pattern 58 is then used as a mask in the etching of the Si₃N₄film 56 x to form the nitride film pattern 56 (FIG. 8(D)). The nitridefilm pattern 56 thus obtained has a hole pattern 64 and part of it isformed more thickly because of the step in the groove 52 formed underthe nitride film pattern 56. In other words, the (nitride film pattern)part 56 a around the side wall of the groove 52 formed on the base oxidefilm 12 is thicker than the (nitride film pattern) part 56 b formed onthe bottom of the groove 52.

Next, the upper oxide film 26 is formed on the base oxide film 12 thatincludes the nitride film pattern 56 (process 3-5) (FIG. 9(A)).

In this embodiment of the present invention, the CVD method is used toform an SiO₂ film, as the upper oxide film 26, to a depth of between 500and 800 nm on the base oxide film (SiO₂ film).

Next, the same etching processing is used to form the wiring groove 28that penetrates the upper oxide film 26 to expose part of the area thatincludes the hole pattern 64 in the nitride film pattern 56 and to formthe hole 30 that penetrates the base oxide film 12 in the hole pattern64 to expose part of the substrate 10 (process 3-6) (FIGS. 9(A) and9(B)).

Therefore, in this example, as in the first and second embodiments,after formation of the resist pattern 34 with the window 32 shaped inthe wiring groove pattern on the upper oxide layer 26 (FIG. 9(A)), thisresist pattern 34 is used as a mask in dry etching.

In this etching process, the upper oxide film 26 is first etched but theetching rate for the area around the side wall of the wiring groove 28is higher than that for the central part of the groove 28. Therefore,when etching of the upper oxide film 26 ends, the bottom of the sidewall of the wiring groove is excessively etched. Also, the etching ofthe upper oxide film 26 ends when the nitride film pattern 56 works as astopper. In this example, the nitride film pattern 56 can be formed sothat the part around the side wall 56 a of the wiring groove 28 isthicker than the part on the bottom of the groove 56 b (near thecenter). Accordingly, even when there has been excessive etching, thebase oxide film 12, which is beneath the area 56 a with the nitride filmpattern, can be protected. Also, a thick nitride film pattern 56 is onlyprovided in areas where there is excessive etching and so the whole ofthe nitride film pattern 56 need not be made thick. Accordingly, thereis no danger of the interconnection capacity of the semiconductor deviceincreasing after manufacture (FIG. 9(B)).

Next, the wiring metal 36 is embedded in the hole 30, part of the areaof the exposed nitride film pattern 56, and in the wiring groove 28(process 3-7) (FIG. 9(C)).

In this example, after the CVD method is used to form a barrier metallayer 35 in the wiring groove 28 and hole 30 formed through dry etching,plating is used to embed Cu as the wiring metal 36 in this wiring groove28 and hole 30. By CMP processing the upper oxide film 26 and the partinto which Cu 36 has been embedded, the surface exposed by the upperoxide film 26 and Cu 36 is flattened and the contacts between lines andmetal lines can be formed (FIG. 9(C)).

As a result, as in the first and second embodiments, in this embodiment,the nitride film pattern 56 with its width W2 is formed so that it isbetween 0.2 and 1.0 m bigger than the width W1 of the wiring groove 28(FIGS. 8(C), 9(C), 10(A) and 10(B)). Therefore, in etching to form thewiring groove 28 and hole 30, after etching of the upper oxide film 26,the nitride film pattern 56 acts as a etching mask to protect the baseoxide film 12, as in conventional methods, so that the base oxide layer12 is not exposed except for within the hole pattern 64.

The nitride film pattern 56 is established only where it is needed onthe base oxide film 12, as in this embodiment, and so the pattern can bemade smaller than in conventional semiconductor devices. Accordingly,the stress on the nitride film pattern 56 can also be reduced. Thisenables deformation of formed holes and cracks in the nitride filmcaused by stress to be avoided.

Fourth Embodiment

With reference to FIGS. 11, 12 and 13, an example of the formation ofthe side wall at the end of the nitride film pattern will be explainedas a fourth embodiment of the present invention.

FIGS. 11 and 12 provide overviews of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. They provide cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line.

FIG. 13(A) and 13(B) show a partial plan view of a semiconductor deviceof the fourth embodiment of the present invention and a cross-sectionalview taken along the line I—I of FIG. 10(A), respectively.

Below, those points that differ from the first, second, and thirdembodiments will be explained and detailed explanation of those pointsthat are the same as the first, second, and third embodiments will beomitted.

Firstly, the base oxide film 12 is formed on the substrate 10 (process4-1) (FIG. 11(A)).

In this example, as in the first through third embodiments of thepresent invention, the CVD method is used to form a SiO₂ film 12 ofbetween 500 and 800 nm in depth on the Si substrate 10.

Next, a nitride film pattern 16 with a hole pattern 14 is formed in thearea that encloses the outside of the wiring groove to be formed later(process 4-2) (FIGS. 11(A) and 11(B)).

In this example, as in the first embodiment, the CVD method is used toform an Si₂N₄ film of between 150 and 300 nm in depth as the nitridefilm 16 x on the SiO₂ film 12. A resist film is then provided on theSi₂N₄ film 16 x and then photo lithography technology is used to form aresist pattern 18 that corresponds to the nitride film pattern (FIG.11(A)). Then, the nitride pattern 16 is formed by etching the Si₂N₄ film16 x using the resist pattern 18 as a mask. In this embodiment, thenitride film pattern 16 is formed from a line pattern 16 a of a width W2that is between 0.2 and 1.0 m larger than the width W1 of the line to belaid in a later process and a hole pattern 14 formed in this linepattern 16 a for contact between lines x.

Next, the nitride film pattern 16 is used as a mask and by etching thearea of the base oxide film 12 exposed from the nitride pattern 16 fromthe surface of this area in the direction of the thicker base oxide film12, at least a groove for formation of the side wall is formed on thebase oxide film exposed from the hole pattern (process 4-3) (FIG.11(B)).

In this example, the nitride film pattern 16 is used as a mask todry-etch the exposed part of the base oxide film 12 to a depth ofbetween 100 and 300 nm and this forms the groove 68 for formation of theside wall. Etching is difficult to control if the depth of the groove 68is less than 100 nm. The side wall created later will also be low andtherefore will be inadequate for acting as an etching stopper. For thisreason, a groove 68 depth of between 100 and 300 nm is preferable. Thegroove for side wall formation 68 is formed in the area 66 y of the baseoxide layer inside the hole pattern provided in the nitride film pattern16. This etching results in the formation of a step 69 between the area66 x of the base oxide film outside the nitride film pattern 16 and theupper surface of the nitride film pattern 16 (FIG. 11(B)).

Next, a groove for side wall formation 68 and a film for side wallformation 70 on the nitride film pattern 16 are formed (process 4-4)(FIG. 11(C)).

In this example, the CVD method is used to form a polysilicon film ofbetween 100 and 300 nm in depth as the side wall film 70 in the groovefor side wall formation 68, on the step 69, on the nitride film pattern16, and on the exposed base oxide film 12 (FIG. 11(C)).

Next, etching of the side wall film 70 is implemented to expose thesurface of the nitride film pattern 16 and thus form the side wall 72 onthe side of the groove 68 for side wall formation (process 4-5) (FIG.11(D)).

Here, anisotropic dry etching using Cl₂ gas (chlorine gas) isimplemented until the surface of the nitride film pattern 16 is exposedfrom underneath the polysilicon film 70. This enables formation of theside wall 72 of the polysilicon film on the side wall of the groove 68for side wall formation formed on the base oxide film 12. Also, the sidewall 13 on the step 69 is formed through etching (FIG. 11(D)).

Next, the upper oxide film 26 is formed on the side walls 72 and 73, onthe base oxide film 12 exposed from the side walls 72 and 73 and on thenitride film pattern 16 (process 4-6) (FIG. 12(A)).

In this example, an SiO₂ film of between 500 and 800 nm in depth isformed, as the upper oxide film 26, on the side walls 72 and 73, and onthe base oxide film 12 exposed from the side walls 72 and 73, and onnitride film pattern 16 (FIG. 12(A)). This upper oxide layer 26 isformed using the CVD method.

Next, the same etching processing is used to continuously form wiringgrooves 28 that penetrate the upper oxide film 26 to expose some of thearea of the nitride film pattern 16 that includes the hole pattern 14and holes 30 that penetrate the base oxide film 12 exposed from the sidewall 72 to expose part of the substrate 10 (process 4-7) (FIG. 12(B)).

In this example, as in the first through third embodiments of thepresent invention, after the resist film is formed on the upper oxidefilm 26 it is patterned to form the resist pattern 34 in which thewiring groove pattern becomes the window 32. This resist pattern 34 isthen used as a mask in dry etching to firstly form a wiring groove 28through the upper oxide film 26. The nitride film pattern 16 is exposedat the bottom of the wiring groove 28. Next, using the nitride filmpattern 16 and the side wall 72 formed in the hole pattern 14 as masks,the base oxide film 12 exposed from the side wall 72 is etched until theSi substrate is exposed. This causes formation of wiring groove 28 andthe hole 30 for the contact between lines (FIG. 12(B)).

Next, the wiring metal 36 is embedded in the hole 30, on the exposedside wall 72, on part of the exposed nitride film pattern 16 area, andin the wiring groove 28 (process 4-8) (FIG. 12(C)).

In this example, as in the first through third embodiments of thepresent invention, after the CVD method is used to form the barriermetal layer 35 in the wiring groove 28 and hole 30, plating is used toembed Cu as the wiring metal 36 in this wiring groove 28 and hole 30.Then, CMP processing of the embedded Cu 36 is implemented to flatten theupper oxide film 26 and the exposed surface of the Cu 36 and to enableformation of the contact between lines and metal lines (FIG. 12(C)).

As a result, as in the first through third embodiments of the presentinvention, the nitride film pattern 16 with its width W2 is formed sothat the perimeter of the pattern 16 is between 0.2 and 1.0 m largerthan the width W1 of the opening of the wiring groove 28 (FIGS. 12(C),13(A) and 13X)). Therefore, in etching to form the wiring groove 28 andhole 30, after etching of the upper oxide film 26 ends, the nitride filmpattern 16 acts as an etching mask to protect the base oxide film 12without exposing it except within the hole pattern 14.

Also, in this embodiment, the nitride film pattern 16 is establishedonly where it is needed on the base oxide film 12 and so the pattern canbe made smaller than in conventional semiconductor devices. Accordingly,the stress on the nitride film pattern 16 can also be reduced. Thisenables deformation of formed holes and cracks in the nitride filmcaused by stress to be avoided.

Also, in this embodiment, particularly during etching of the base oxidefilm 12, thought has been placed into the design of the structure of thebase oxide film 12 around the end (opening) of the hole pattern 14,where durability in etching of the nitride film pattern that acts as themask is low. That is, immediately after formation of the nitride filmpattern 16, this nitride film pattern 16 is used as a mask and a groove68 for side wall formation is prepared in the area intended for holeformation in the base oxide film 12 (refer to FIG. 11(B)). On thisgroove 68 for side wall formation, a side wall 72 made of a polysiliconfilm that has a higher etching selection ratio for an SiO₂ film than fora nitride film is formed (FIG. 11(D)). Thus, in the etching of the baseoxide film 12 when the hole is formed, the side wall 72 becomes the maskand the area of the base oxide film 12 exposed from the side wall 72 isetched. This means there is no danger of excessive etching at the end ofthe nitride film pattern 16. Also, for example, when the hole diameterin the hole pattern 14 of the nitride film pattern 16 is as small as canbe for hole formation using photo lithography, holes with an evensmaller diameter can be formed.

Fifth Embodiment

With reference to FIGS. 14, 15 and 16, an example of the formation ofthe nitride film pattern using a side wall that differs from the fourthembodiment will be explained as a fifth embodiment of the presentinvention.

FIGS. 14 and 15 provide overviews of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. They provide cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line.

FIGS. 16(A) and 16(B) show a partial plane view of a semiconductordevice of the fifth embodiment of the present invention and across-sectional view taken along the line I—I of FIG. 16(A),respectively.

Below, those points that differ from the first through fourthembodiments will be explained and detailed explanation of those pointsthat are the same as the first through fourth embodiments will beomitted.

Firstly, the base oxide film 12 is formed on the substrate 10 (process5-1) (FIG. 14(A)).

In this example, as with the first through fourth embodiments, the CVDmethod is used to form an SiO₂ film of between 500 and 800 nm in depthon the Si substrate 10.

Next, a groove 52 with an opening shape the same as for the wiringgroove formed later is formed (process 5-2) (FIG. 14(A)).

In this example, as in the third embodiment, a groove 52 of the sameshape and size (opening diameter) as the wiring groove established lateris formed to a depth of between 100 and 300 nm through photo lithographyfollowed by etching (FIG. 14(A)). As in the fourth embodiment, the depthof this groove 52 is determined after consideration of etchingcontrollability and the side wall to be formed later.

Next, a film 74 for the side wall is formed on the base oxide layer thatincludes the groove 52 (process 5-2) (FIG. 14(B)).

In this example, the CVD method is used to form a polysilicon film ofbetween 100 and 300 nm in depth as the side wall film 74 on all thesurfaces of the base oxide film 12 including the groove 52 (FIG. 14(B)).

Next, by etching to expose the surface of the base oxide film 12 in theside wall film 74, the side wall 76 is formed on the side wall of thegroove 52 (process 5-4) (FIG. 14(C)).

In this example, anisotropic dry etching of the polysilicon film 74 isimplemented using Cl₂ gas until the surface of the base oxide film 12,not including the groove, and the bottom of the groove 52 are exposed.This causes formation of a polysilicon film side wall 76 on the sidewalls of the groove 52 (FIG. 14(C)).

Next, a nitride film pattern 56 with a hole pattern 64 is formed on theside wall 76, in the groove 52 exposed from the side wall 76, and on thebase oxide film 12 surrounding this groove (process 5-5) (FIGS. 14(D))through 12(A)).

Here firstly, the CVD method is used to form a nitride film (Si₃N₄ film)56 x of between 150 and 300 nm in depth on the groove 52, which includesthe side walls 76, and on the base oxide film 12 (FIG. 14(D)). A resistfilm is then provided on this Si₃N₄ film 56 x and photo lithographytechnology is used to form a resist pattern 58 that corresponds to thenitride film pattern. This resist pattern 58 is then used as a mask inthe etching of the Si₃N₄ film 56 x. The part of this Si₃N₄ film 56 xthat remains after etching forms the nitride film pattern 56. Thisnitride film pattern 56 is formed within the groove 52 and on thesurface of the area of the base oxide film 12 around this groove 52. Thenitride film pattern 56 thus obtained comprises a line pattern of awidth W2 that is between 0.2 and 1.0 μm larger than the width W1 of theline to be established in a later process, and a hole pattern 64 forcontact between lines that is formed within this line pattern (FIG.15(A)).

Next, the upper oxide film 26 is formed on the base oxide film 12 thatincludes the nitride film pattern 56 (process 5-6) (FIG. 15(B)).

In this example, the CVD method is used to form an SiO₂ film of between500 and 800 nm in depth as the upper oxide film 26 on the base oxidefilm 12 that includes the nitride film pattern 56 (FIG. 15(B)). Thisupper oxide film 26 is formed using the CVD method.

Next, the same etching processing is used to continuously form wiringgrooves 28 that penetrate the upper oxide film 26 to expose part of thenitride film pattern 56 that includes the hole pattern 64 and holes 30that penetrate the base oxide film 12 in the hole pattern 64 to exposepart of the substrate 10(process 5-7) (FIG. 15(C)).

In this example, as in the first through fourth embodiments of thepresent invention, after the resist film is formed on the upper oxidefilm 26 it is patterned and a resist pattern 34 with the wiring groovepattern as its window 32 is formed. This resist pattern 34 is then usedas a mask in dry etching to firstly form the wiring groove 28 on theupper oxide film 26. Next, the nitride film pattern 56 is used as a maskto etch the base oxide film 12 exposed from the hole pattern 64 untilthe Si substrate 10 is exposed. Through this process the hole 30 for thecontact between lines is formed (FIG. 15(C)).

Next, the wiring metal 36 is embedded into the hole 30, on part of theexposed nitride film pattern 56 area, and in the wiring groove 28process 5-8) (FIG. 15(D)).

In this example, as in the first through fourth embodiments, after theCVD method is used to form the barrier metal layer 35 in the wiringgroove 28 and the hole 30, plating is used to embed Cu as the wiringmetal 36 in this wiring groove 28 and hole 30. CMP processing of thepart into which Cu 36 is embedded then takes place to flatten the upperoxide film 26 and the exposed Cu 36 surface. The contact between linesand metal lines can then be formed (FIG. 15(D)).

As a result, as in the first through fourth embodiments of the presentinvention, a nitride film pattern 56 with its width W2 is formed so thatit is between 0.2 and 1.0 μm larger than the diameter W1 of the openingof the wiring groove 28 (FIGS. 15(D), 16(A) and 16(B)). This means thatin etching to form the wiring groove 28 and hole 30, after etching ofthe upper oxide film 26 ends, the nitride film pattern 56 acts as anetching mask to protect, as in conventional methods, the base oxide film12 without exposing any of the base oxide film 12 except within the holepattern 64.

Also, the nitride film pattern 56 is established only where it is neededon the base oxide film 12, as in this embodiment, and so the pattern canbe made smaller than in conventional semiconductor devices. Accordingly,the stress on the nitride film pattern 56 can also be reduced. Thisenables deformation of formed holes and cracks in the nitride filmcaused by stress to be avoided.

After the upper oxide film 26 has been formed on the base oxide film 12,which includes the nitride film pattern 56, the wiring groove 28 isformed through the upper oxide film 26 and, at the same time, etching toform the hole 30 for contact between lines on the base oxide film 12 isimplemented. At this time the resist pattern 34 that corresponds to theshape of the wiring groove is formed on the upper oxide film 26. Even ifa slight discrepancy in the position of the resist pattern 34 emerges,the side wall 76 lies beneath the part of the nitride film pattern 56exposed from the formed wiring groove 28 and therefore the film is thickhere. Thus, as is preferable, the area of the base oxide film 12positioned beneath the nitride film pattern 56 can be protected.

Sixth Embodiment

With reference to FIGS. 17, 18 and 19, a modified example of the firstembodiment will be explained as a sixth embodiment of the presentinvention.

FIGS. 17 and 18 provide overviews of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. They provide cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line. FIGS. 19(A) and 19(B) show apartial plan view of a semiconductor device of the sixth embodiment ofthe present invention and a cross-sectional view taken along the lineI—I of FIG. 19(A), respectively. FIG. 20 is a general schematic view ofthe mask used in photo lithography.

Below, those points that differ from the first through fifth embodimentswill be explained and detailed explanation of those points that are thesame as the first through fifth embodiments will be omitted.

Firstly, as in the first embodiment of the present invention, the baseoxide film 12 is formed on the substrate 10 (same as process I—I) (FIG.17(A)). In this example, the CVD method is used to form a SiO₂ film ofbetween 500 and 800 nm in depth as the base oxide film 12 on the Sisubstrate.

Next, a nitride film pattern 16 with a hole pattern 14 is formed on thebase oxide film 12 (similar to process 1-2) (FIGS. 17(A) and 17(B)).

In this example, firstly the CVD method is used to form an Si₃N₄ film of50 nm in depth as the nitride film 16 x on the SiO₂ film 12. A resistfilm is then provided on the Si₃N₄ film 16 x and using ordinary photolithography technology, a resist pattern 80 is formed to correspond tothe nitride film pattern (FIG. 17(A)).

The configuration of the mask 82 used in this photo lithography is shownin FIG. 20. This mask 82 comprises a transparent mask substrate 84, aline pattern 86 of a width that is, in practice, the same as the widthW1 of the line to be made later, and a hole pattern 88 for the contactbetween lines. There is a plurality of line patterns 86 and thesepatterns run parallel to one another. There are also as many holepatterns 88 as required. In this example, the line width W1 is between0.25 and 1.0 μm and the hole diameter is between 0.1 and 0.5 μm. Thehole diameter is designed so that it is never larger than the line widthW1.

In this example, etching of the resist film with this mask 82 is used toform the resist pattern 80 that corresponds to the shape of the nitridefilm pattern (FIG. 17(A)). Then, by etching the Si₃N₄ film 16 x usingthis resist pattern 80 as the mask, the nitride film pattern 16 isformed with the same size and shape as the wiring groove width W1 andwith the hole pattern 14 (FIG. 17(B)).

Next, the upper oxide film 26 is formed on the base oxide film 12 tocover the nitride film pattern 16 (same as process 1-3) (FIG. 17(C)).

In this example, the CVD method is used to form an SiO₂ film of between500 and 800 nm in depth as the upper oxide film 26 on the base oxidefilm 12 (FIG. 17(C)).

Next, the same etching processing is used to continuously form wiringgrooves 28 that penetrate the upper oxide film 26 to expose the nitridefilm pattern 16 and, using the nitride film pattern 16 as a mask, holes30 that penetrate the base oxide film 12 to expose part of the substrate10 (modification of process 1-4) (FIGS. 18(A) and 18(B)).

In this embodiment, after the resist film has been formed on the upperoxide film (SiO₂ film) 26 it is patterned to form a resist pattern 34 inwhich the wiring groove pattern becomes the window 32. Next, the resistpattern 34 is used as a mask in dry etching that uses a reaction gasincorporating CH₂F₂ gas. Here, the upper oxide film 26 exposed from thewindow 32 is etched using a gas in which C₄F₈, O₂, Ar, and CH₂F₂ areincorporated with flow rates of 20, 6, 400, and 10 sccm respectively.Etching of the upper oxide film 26 ends when the surface of the nitridefilm pattern 16 that lies between the upper oxide film 26 and the baseoxide film 12 is exposed. When CH₂F₂ is incorporated in the reactiongas, the reaction product adheres to everything from the internal wallsurface of the wiring groove formed by etching to the nitride filmpattern 16 on the bottom of the groove. This causes tapering of theinternal wall surface of the wiring groove 28 formed (FIG. 18(A)). Thenitride film pattern 16 that is exposed from the bottom of the openingof the upper oxide film 26 is then used as a mask in etching the baseoxide film 12 that is exposed from the hole pattern 14. The reactionproduct produced through etching the upper oxide film 26 adheres to thenitride film pattern 16 (not shown in any figure) and this acts as aprotective film. Accordingly, the nitride film pattern 16 is not asthick (50 nm) as normal (150 to 300 nm) but is adequate for use as amask in forming the above protective film. The etching of the base oxidefilm 12 ends when the surface of the Si substrate 10 is exposed from thehole pattern 14. This causes formation of the wiring groove 28 and hole30 (FIG. 18(B)).

Next, the portion of the nitride film pattern 16 exposed in the wiringgroove 28 is etched and removed. In this embodiment of the presentinvention, a combination or mixture of CHF₃ and CF₄ is used as theetching gas. So that the base oxide film 12 below is not etched, etchingis implemented so that the nitride etching selection ratio is high forthe oxide film. Accordingly, a CHF₃ rich mix, that is a mix with aCHF₃:CF₄ ratio of 3:1 (flow rate ratio) is used. Through the use of suchconditions it is possible to ensure a nitride film etching selectionratio of approximately 5 for the oxide film. This enables removal of theportion 16 y of the nitride film pattern 16 exposed from the wiringgroove 28 (FIG. 18(C)).

Next, the wiring metal 36 is embedded into the hole 30 and wiring groove28 (same as process 1-5: dual damascene process) (FIG. 18(D)).

In this example, for example after the CVD method is used to form a 50nm barrier metal layer 35 in the hole 30 and groove 28, plating is usedto embed Cu 36 in the hole 30 and wiring groove 28. When the hole 30 hasbeen filled by the barrier metal layer 35, Cu 36 can be embedded just inthe wiring groove 28 in which case the spatter method can be used. Also,in this example, Cu has been used as the wiring metal 36 to reduce theline capacity but the lines and contacts between lines can also be madeusing an Al alloy as the metal.

CMP processing of the part in which the Cu 36 is embedded is thenimplemented to enable formation of the contact between lines and themetal lines (FIG. 18(D)).

As a result, as is clear from the above explanations, the nitride filmpattern 16 with its width W2 is formed so that it is of the same size asthe opening of the wiring groove 28 and so that it is thinner than usual(FIGS. 18(D), 19(A) and 19(B)). Also, in the etching to form the wiringgroove 28 and hole 30, a gas incorporating CH₂F₂ is used. Thus, thewiring groove 28 is tapered after its formation. After etching of theupper oxide film 26 ends, the nitride film pattern acts as an etchingmask to protect the base oxide film 12 so that none of this base oxidefilm 12 is exposed except within the hole pattern 14.

Also, the nitride film pattern 16 is established only where it is neededon the base oxide film 12 and so the pattern can be made smaller than inconventional semiconductor devices. In addition, it is not as thick asthe film used in conventional methods. Accordingly, the stress on thenitride film pattern 16 can also be reduced. This enables deformation offormed holes cracks in the nitride film caused by stress to be avoided.

In this embodiment, a mixture of C₄F₈, O₂, Ar, and CH₂F₂ is used as thereaction gas in etching to form the wiring grooves and holes. However, agas in which CH₂F₂ is mixed with three or four of C₄F₈, O₂, Ar, and COcan also be used. For example, combinations such as C₄F₈, O₂, Ar, CO andCH₂F₂ or C₄F₈, Ar, CO and CH₂F₂ are possible.

Also, in this embodiment, a combination of CHF₃ and CF₄ gas has beenused in etching to remove the nitride film pattern exposed from thewiring groove. However, as a fluorine gas, SF₆ can also be used. Toincrease the nitride film etching selection ratio for the oxide film,the amount of the O₂ gas added to the etching gas can be reduced.

The process to remove the portion 16 y of the nitride film pattern 16exposed from the wiring groove 28 is only implemented in this embodimentof the present invention but can also be applied in the first throughfifth embodiments.

Seventh Embodiment

The seventh embodiment of the present invention is an example of amodification to the sixth embodiment. An example of modifications to thefirst embodiment will be explained with reference to FIG. 21.

FIG. 21 provides an overview of the processes involved in themanufacture of the semiconductor devices of this embodiment of thepresent invention. It provides cross sections taken at positions on thestructure during manufacture that have both a hole for the contactbetween lines and a groove for line.

FIGS. 22(A) and 22(B) show a partial plane view of a semiconductordevice of the seventh embodiment of the present invention and across-sectional view taken along the line I—I of FIG. 22(A),respectively.

Below, those points that differ from the sixth embodiment will beexplained and detailed explanation of those points that are the samewill be omitted.

Firstly, as in the sixth embodiment of the present invention, after thebase oxide film 12 is formed on the substrate 10, a nitride film pattern16 with a hole pattern 14 is formed on the base oxide film 12 (refer toFIGS. 17(A) and 17(B)). An upper oxide film 26 is then formed on thebase oxide film 12 to cover the nitride film pattern 16 (refer to FIG.17(C)). Next, the same etching processing is used to continuously formwiring grooves 28 that penetrate the upper oxide film 26 to expose thenitride film pattern 16 and holes 30 that penetrate the base oxide film12 to expose part of the substrate 10 using the nitride film pattern 16as a mask (refer to FIGS. 18(A) and 18(B)).

Next, the part of the nitride film pattern 16 that is exposed in thewiring groove is etched and removed. In this embodiment, wet etching isused here. Wet etching is implemented with a high nitride film etchingselection ratio for the oxide film. In this example, H₃PO₄ is used asthe etchant.

Firstly, the H₃PO₄ is placed inside the etching tank in which wetetching will take place and then heated to 160° C. Next, the structureas shown in FIG. 18(B) is immersed in the H₃PO₄ in the etching tank. Inthis example, the thickness of the nitride film pattern is 50 nm. Thenitride film etching rate achieved by the H₃PO₄ is approximately 60 nmper minute. This means that the immersion time is approximately oneminute. The structure is then washed in pure water and dried.

This process enables removal of almost all the nitride film pattern 16that lies between the base oxide film 12 and the upper oxide film 26(FIG. 21(A)).

Next, as in the sixth embodiment, the wiring metal 36 is embedded in thehole 30 and wiring groove. Firstly, after the CVD method is used to formthe barrier metal layer 35 in the hole 30 and wiring groove 28, platingis used to embed Cu 36 in the hole 30 and wiring groove 28. Byimplementing CMP processing from the top of the upper oxide film 26until its upper surface is exposed, the contacts between lines and metallines can be formed (FIG. 21(B)).

Accordingly,as shown in FIGS. 21(B), 22(A) and 22(B), barrier and wiringmetal (35, 36) that fills each of the holes (3) and each of the wiringgrooves (28), the barrier and wiring metal (35, 36) having first portion(37 a) on the base oxide film (12) and second portions (37 b) at amiddle section of the upper oxide film (26) above the first portions (37a), and each of the first portions (37 a) having a with W1 than a widthw3 of each of the second portions (37 b).

As a result, the nitride film is removed from the structure after theline is formed. This configuration allows deformation of the holesformed and cracks in the nitride film caused by stress placed on thenitride film to be avoided. It also enables a large reduction in theline capacity as there is no interference by the nitride film.

In this embodiment of the present invention, the etchant used inremoving the nitride film pattern 16 that is exposed from the wiringgroove 28 is H₃PO₄. However, this is not the only etchant that can beused. Any other etchant that can ensure that the nitride film etchingselection rate is high for the oxide film can be used.

Also, the process to remove the nitride film pattern 16 that is exposedfrom the wiring groove 28 using wet etching is only implemented in thisembodiment but it can also be applied to the first through fifthembodiments.

Eighth Embodiment

An example of a semiconductor device configured so that a base wiringarea is formed on the upper surface of a underlayer of the semiconductordevice formed in the first through seventh embodiments of the presentinvention will be explained as an eighth embodiment.

FIG. 23 is a general diagram of the processing that relates to substrateuntil before the base oxide film is formed on a underlayer. The diagramprovides cross sectional views.

In this embodiment, a base wiring area 90 is formed on the upper surface10 a of the substrate 10 as an underlayer. This base wiring area 90 isprovided with a barrier metal 92 on the inside wall of the contact hole91 provided on the substrate 10. Cu, the wiring metal 94, is formed sothat it fills the contact hole 91 on this barrier metal 92. In thisexample, the thickness of the wiring metal 94 is between 500 and 600 nm(FIG. 23(A)).

A dispersion prevention film 95 is formed across the entire uppersurface 10 a of this substrate 10. In this example, the dispersionprevention film is a silicon nitride film. The CVD method is used toform a film to a depth of between 30 and 50 nm (FIG. 23(B)).

Next, this dispersion prevention film 95 is patterned until dispersionprevention film 95 x only remains on the base wiring area 90 of thesubstrate 10.

In this embodiment, after a resist pattern 96 is formed on thedispersion prevention film 95 to cover the base wiring area 90 (FIG.23(C)), the resist pattern 96 is used as a mask in anisotropic dryetching to remove the dispersion prevention film 95. An etching gas suchas a mixture of CHF₃ and CO is used.

Then, removal of the resist pattern 96 achieves a substrate 10 withdispersion prevention film 95 x only on the base wiring area 90(FIG.23(D)).

As explained for the first through seventh embodiments for the presentinvention, a base oxide film is formed on the substrate 10 that includesthe dispersion prevention film 95.

On the upper surface 10 a of the substrate 10 a on which the base wiringarea 90 is formed as in this embodiment, the dispersion prevention film95 x is only provided over the base wiring area 90. Therefore, thecapacity between the substrate 10 and the base oxide film provided aboveit can be minimized. Thus, by combining this embodiment with any of thefirst through seventh embodiments, the overall line capacity of thesemiconductor device can be reduced. Also, the effects of stress on thenitride film can be greatly reduced compared to conventional methods.

As made clear in the above explanations, the semiconductor device of thepresent invention is provided with a underlayer, a base oxide filmformed on top of this underlayer, a nitride film pattern with a holepattern that is provided on top of this base oxide film, a hole thatpenetrates the above base oxide film, an upper oxide film provided onthe base oxide film to cover the nitride film pattern, a wiring groovein which part of the nitride film pattern placed on the upper oxide filmand including a hole pattern is exposed, and wiring metal that fills theholes and wiring groove. The above nitride film pattern is formed to beof a shape and size that enables it to enclose the outside of the wiringgroove. This nitride film pattern does not touch any neighbouringnitride film pattern.

Therefore, the size of the nitride film pattern can be smaller than inconventional semiconductor devices and the stress on the nitride filmreduced. This produces a semiconductor device with low interconnectioncapacity.

Also, methods for manufacturing semiconductor devices with small nitridefilm patterns than in conventional devices include the followingprocesses: a process to form a base oxide film on the substrate (1-1); aprocess to form a nitride film pattern with a hole pattern on the baseoxide film (1-2); a process to form an upper oxide film on the baseoxide film to cover the nitride film pattern (1-3); a process where thesame etching is used to form, one after another, the wiring groove thatpenetrates the upper oxide film to expose the nitride film pattern, andthe hole that, when the nitride film pattern is used as a mask,penetrates the base oxide film to expose part of the substrate (1-4);and a process to fill the hole, part of the exposed nitride filmpattern, and the wiring groove with the wiring metal (1-5).

In the above process (1-2), a nitride pattern of a shape and size thatencloses the outside of the wiring groove is formed. When wiring groovesand holes are continuously formed (process 1-4), this nitride filmpattern is used as a mask to form holes with openings that are smallerthan that of the wiring groove. That is, the nitride film pattern is amask that covers the upper surface of the base oxide film except forwhere holes will be formed. Here, the nitride film pattern should coverthe area other than where holes will be formed on the base oxide filmthat has been exposed from the wiring groove. Accordingly, by forming anitride film pattern, which is easily subject to stress, over aminimized area, the stress can be reduced. Therefore, deformation offormed holes and cracks in the nitride film caused by stress can beavoided.

What is claimed is:
 1. A semiconductor device, comprising: anunderlayer; a base oxide film with first holes and formed on theunderlayer; a groove having a sidewall formed in said base oxide filmaround respective ones of said first holes; a plurality of nitride filmpatterns, each having a hole pattern, respectively, formed on the baseoxide film and directly connected to said first holes, respectively; anupper oxide film provided on top of said base oxide film to cover thenitride film patterns, the upper oxide film having formed therethrough aplurality of wiring grooves which each reaches part of an associatednitride film pattern including said hole patterns; and wiring metal thatfills said first holes, and said wiring grooves; and wherein saidnitride film patterns are separate from each other and have a shape andsize that extends from the outside of their associated wiring groove. 2.A semiconductor device according to claim 1 wherein said nitride filmpattern is formed with such a shape and size that surrounds the outsideof said wiring groove with a gap from 0.2 to 1.0 μm.
 3. A semiconductordevice, comprising: an underlayer; a base oxide film with first holesformed on the underlayer; a plurality of nitride film patterns on thebase oxide film, the nitride film patterns having formed therethroughhole patterns, respectively, which are formed directly connected to andwider than said first holes respectively; an upper oxide film providedon top of said base oxide film to cover the nitride film patterns, theupper oxide film having formed therethrough a plurality of wiringgrooves which each exposes part of the nitride film patterns includingsaid hole patterns; and wiring metal that fills part of each of theexposed nitride film patterns, each of said first holes, each of saidhole patterns, and each of said wiring grooves; and wherein an outershape of each of said nitride film patterns is substantially the same asthe shape of the opening of each of said wiring grooves, an internalwall surface of each of said wiring grooves is tapered from the openingon an upper surface of said upper oxide film to upper surface of each ofsaid nitride film patterns, and neighbouring nitride film patterns areseparate from each other.
 4. A semiconductor device, comprising: anunderlayer; a base oxide film formed on the underlayer, the base oxidefilm having formed therethrough a plurality of first holes; an upperoxide film provided on the base oxide film, the upper oxide film havingformed therethrough wiring grooves which are connected to said firstholes, respectively; and barrier and wiring metal that fills each ofsaid first holes and each of said wiring grooves, said barrier andwiring metal having a first portions on the base oxide film and secondportions at a middle section of said upper oxide film above said firstportions, and each of said first portions having a width W1 wider than awidth W3 of each of the second portions.
 5. A semiconductor deviceaccording to claim 1, wherein part of the upper surface of saidunderlayer constitutes the base wiring area, said hole reaches the basewiring area, and a dispersion protection film is formed only on saidbase wiring area outside the hole.
 6. A semiconductor device accordingto claim 2, wherein part of the upper surface of said underlayerconstitutes the base wiring area, said hole reaches the base wiringarea, and a dispersion protection film is formed only on said basewiring area outside the hole.
 7. A semiconductor device according toclaim 3, wherein part of the upper surface of said underlayerconstitutes the base wiring area, said hole reaches the base wiringarea; and a dispersion protection film is formed only on said basewiring area outside the hole.
 8. A semiconductor device according toclaim 3, wherein part of the upper surface of said underlayerconstitutes the base wiring area, and a dispersion protection film isformed only on said base wiring area outside the hole.
 9. Thesemiconductor device of claim 1, wherein said nitride film patterns areformed in said groove and have a portion around said sidewall that isthicker than a portion in a bottom of said groove.
 10. The semiconductordevice of claim 1, further comprising a sidewall film formed on thesidewall of said groove.
 11. The semiconductor device of claim 10,wherein said sidewall film has a higher etching selection ratio for anSiO₂ film than for a nitride film.